It is common and required by regulation or law that industrial and agricultural vehicles used on highways have signal lamps. Typical constructions of such signal lamps are shown in U.S. Pat. Nos. 3,564,483, 3,666,940, Des. 216,915 and Des. 216,914 and comprise a housing having an annular wall and a lens with a front wall and a peripheral wall telescoped over the annular wall.
Established photometric standards such as United States S.A.E. J 96 and J 974 require that the lamp emit minimum candlepower in a direction at 90.degree. to the axis of the lens. More specifically, these standards require a projection of four candlepower at 90.degree.. This standard is difficult to meet and comply with.
An important aspect of the present invention is to provide a warning lamp which meets the photometric standards and provides required light in a direction at 90.degree. to the axis of the lamp lens.
In accordance with the invention, a prism is provided along at least opposed side portions of the peripheral wall of the lens which is constructed and arranged to redirect light from the filament of the bulb in a direction generally at 90.degree. to the axis of the lens.